Method for producing burnable gases for thrust engines

ABSTRACT

Burnable gases under pressure for operating engines such as thrust engines and particular rocket and ramjet engines are produced by arranging together two solid propellant charges, one of which comprises an auxiliary propellant charge having a high thermal efficiency and the other constituting a main propellant charge comprising a material of low heat of fusion and evaporation. The auxiliary charge is ignited by a fuse device and will burn off adjacent the main charge but shielded therefrom by a burn-off insulation. The burnable gases which are produced are directed by their own pressure through a gas duct into a combustion chamber where they are admixed with an oxidizer which may be supplied under the pressure force of the gases themselves.

O Umted States Patent 1111 3,595,020

[72] Inventors .IohannesSchubert [50] Fieldot'Search 60/39.l2

Unterhaching; R611 Fuchs, Poing, both 61, Germany 1 References Cited 21 A 1.N6. 28,201 UNITEDSTATES PATENTS 1221 PM APT-144970 2,816,419 12/1957 011161161 .4 60/39.48X 4s Patented Ju1 27.197l 3,086,354 4/l963 11311 60/25IX (731 cesel'schm 3,107,485 10/1963 Toucmin 60 251 $$L 3,349,562 lO/1967 Williamsetal.............., 60/39.48X

1 3 Priority 8, 6 3, 50,887 11/1967 Leumgetal 60/25l 33 Germany Primary Examiner -Douglas Hart 3 B 39 40 Att0rneyMcGlew and Toren Continuation of application Ser. No. 671,658, Sept. 29, 1967, now abandoned.

[54] METHOD FOR PRODUCING BURNABLE GASES FOR THRUST ENGINES 4 Claims, 6 Drawing Figs.

[52] US. Cl 60/204, 60/39.02, 60/39.12, 60/39.48, 6059.49, 60/209,

[5 1] Int. Cl F02k 7/08, F02k 9/02 ABSTRACT: Burnable gases under pressure for operating engines such as thrust engines and particular rocket and ramjet engines are produced by arranging together two solid propel- PATENTED JUL 27 Bil 'Illllla'lllll SHEEI 1 OF 2 INVENYORE; Johannes Schubert By Rolf Fuchs [WA/1b", A11 o RNEYS PATENTEDJumran 3,595.02Q

sum 2 or 2 INVENTORS Johannes Schubert Rolf Fuchs WWW W ATTORNEYS METHOD FOR PRODUCING BURNABLE GASES FOR THRUST ENGINES This is a continuation of application Ser. No. 671,658, filed Sept. 29, l967, now abandoned.

SUMMARY OF THE INVENTION This invention relates, in general, to a method of generating and utilizing bumable gases and to thrust engines for using such gases, and in particular, to a new and useful method and device for effecting the burning of an auxiliary charge ofhigh thermal cfficiency adjacent a main propellant charge of a material of low heat of fusion and evaporation in a manner such that the gases generated are permitted to flow under their own pressure into a combustion chamber for combining with additional oxidizer to effect complete combustionv The method of the invention for producing burnable gases under pressure for thrust engines is particularly applicable to rocket and ramjet engines. The gases are produced from a combination of two solid propellant charges, namely an auxiliary propellant charge with preferably compensated oxygen balance and from a low oxygen or oxygen-free main propellant charge. It is generally known in rocket engineering that liquid fuel components can be conveyed from a storage tank into a combustion chamber utilizing the pressure generated by the composition of an auxiliary propellant charge. It is also known how to transfer solid fuel-rich propellant charges into a fuel gas usable with lithergole engines by partial combustion using an under supply of oxygen. The fuel gas is conveyed to a combustion chamber and then burned completely as it is mixed with air or another oxidizer. ln solid fuel engines'the propellant charge is arranged with a predetermined mixture ratio in the combustion chamber. In lithergole engines, such an arrangement using single stage combustion brings about an uneven mixture formation and hence an unstable irregular combustion which results in a reduction of the efficiency of the engine. For this reason, in the known lithergole engines the solid fuel-rich propellant charge is located outside the combustion chamber where it is preburned with a small quantity of air or oxidizer and then is directed into the main combustion chamber in which the main combustion takes place. For the main combustion the partially burned relatively low energy fuel gas will be employed.

The method of transforming fuel-rich solid propellant charges into fuel gas by partial combustion has the disadvantage that this partial combustion with a pronounced air or oxidizer deficiency and operable as a low-temperature process is difficult to stabilize. The combustion proceeds much too slowly, and moreover the combustion chamber receives preburned and hence relatively low energy fuel gases which adversely affects the efficiency of the engine. In addition, in a low-temperature process, soot is formed which burns very poorly and can be conveyed away only partially as it tends to bake.

In accordance with the present invention, the method avoids the above-mentioned disadvantages and produces a high energy bumable gas from suitable solid propellants. The propellant charge comprises an auxiliary propellant charge of high thermal efficiency and a main propellant charge of a material of low heat and fusion and evaporation, for example, polyethylene, paraffins with more than eight carbon atoms, paraffin derivatives such as wax and alcohols, and acids such as steric acids and paraffin acids and the esters of nitric acid. The auxiliary and the main charges are arranged such that the main charge is fused by the burn-off of the auxiliary propellant chargeaand it is evaporated or sublimated or cracked during this process. During the burn-off of the auxiliary propellant charge therefore its heat acts on the main propellant charge so that it melts and gasities this charge in a manner similar to the heating of a wax ofa candleas it burns. The formed bumable gases are conveyed through connecting lines into the combustion'chamber by the pressure formed by the burn-off of the auxiliarypropellant charge and the resultant gases are burned in a combustion chamber with air or oxygen to create thrust gases directed through an expansion nozzle of a thrust engine. In the application of the invention method to lithergole engines, the pressure created by the auxiliary propellant charge is used to press the liquid oxidizer into the combustion chamber for ignition with the gases which are produced.

To achieve a good heat transfer from the auxiliary propellant charge to the main propellant charge, the auxiliary propellant charge is advantageously embedded in the main propellant charge in the manner ofa wick ofa candle or in one or more layers which are arranged to increase the common surfaces of the two propellant charges for the purposes of im proving and accelerating the heat transfer from the auxiliary propellant charge to the main propellant charge. ln addition, in order to obtain a specified thrust, the invention contemplates the arrangement of different auxiliary propellant charges or main propellant charges in various successively arranged laycrs, which are oriented to provide for the type of burn-off desired and the thrust characteristics which must be obtained.

A particular advantage of the invention is that by a favorable burn-off condition of the auxiliary propellant charge, a

. uniform classification of the main propellant charge is obtained, and thus the high cfficiency of the overall process is assured. The main propellant charge need only be fused or evaporated and sublimated and no chemical reaction need take place which requires heat. Because the auxiliary propellant charge is used for conveying the bumable gases to the combustion chamber, it is assured that these high-energy burnable gases will be delivered in a quantity corresponding to the supplied air or oxidizer in an optimum mixture, and thereafter excellent burnout and high performance of the engine will be assured.

Accordingly, it is an object of this invention to provide an improved method for producing burnable gases under pressure for engines which comprises arranging an auxiliary propellant charge of a high thermal efficiency directly adjacent a main propellant charge ofa material of low heat of fusion and evaporation and igniting the auxiliary propellant charge to cause its burn-off sufficiently close to the main propellant charge so that the main propellant charge is evaporated or sublimated, and conveying the gases thus formed under a pressure conveying force supplied by the burn-off of the gases of the auxiliary charge into a combustion chamber for additional burning.

A further object of the invention is to provide a method of generating and using bumable gases wherein the gases formed by the burn-off of a main charge are conducted by the force of the burn-off of an auxiliary charge through a conduit and into a combustion chamber which is supplied with oxygen which is conveyed to the combustion chamber under the conveying force of the pressure of the auxiliary charge, or the gases are conducted into an engine in which air is admitted for completing the burning thereof. 1

A further object of the invention is to provide an apparatus for producing bumable gases and for burning these gases to produce thrust which includes a main and auxiliary charge arranged together so that the auxiliary charge will burn off at a faster rate and sublimate the main charge, and conduit means for conducting the gases thus formed under the pressure of the auxiliary charge gas burn-off into a combustion chamber having means for adding an oxidizer thereto,

A further object of the invention is to provide a missile rocket or ramjet thrust gas producing device which includes a main charge and an auxiliary charge arranged together and of material such that the auxiliary charge will have a relatively rapid burn-off to cause a sublimation of the main charge and the movement of the gases thus produced into a combustion chamber and wherein the pressure forces of the gases created by the burn-off are used to pump an oxidizer into the combustion chamber or the gases are directed into a combustion chamber in which air is admitted such as by the action of air passing through the device during a flight when incorporated in an-objec'tsuchas a flying body or missile.

A further object of the invention is to provide an apparatus for producing thrust gases for thrust engines which are simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings:

FIG. 1 is a partial elevational and partial longitudinal sectional view of a lithergole engine constructed in accordance with the invention;

FIG. 2 is a view similar to FIG. 1 of a missile having ramjet engines and constructed in accordance with the invention; and

FIGS. 3 to 6 are enlarged transverse sectional views of combinations of auxiliary and main propellant charges arranged in accordance with various modifications of the arrangement indicated in FIG. 1 and 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS Referring to the drawings, in particular, the invention em bodied therein as indicated in FIG. I is incorporated on a missile generally designated 40 which carries a solid fuel combustion charge generally designated 42 in a central area thereof.

In accordance with the invention, the propellant charge 42 comprises a main propellant charge I and an auxiliary propellant charge 3 which is separated from the main charge by a burn-off insulation 2. The auxiliary propellant charge presents a high thermal efficiency and will burn off relatively rapidly in respect to the main charge 1. The main charge 1 comprises a material of low heat or fusion and evaporation, for example, polyethylene, paraffins having more than eight carbon atoms, paraffin derivatives such as wax and alcohols, acids such as steric and paraffin acids and their esters of nitric acid. The auxiliary propellant charge 3 is ignited by a fuse device (not Shown) and it burns off as a front burner. The resultant heat melts and evaporates the contiguous main propellant charge 1. By this process, which is similar to the burn-off ofa candle, burnable gases are produced which are passed through a col lecting chamber 9 arranged below the charge 42 and directed by their own pressure force into a conveying duct for conduit 4 for delivery through a discharge aperture 5 provided at the opposite end thereofinto a combustion chamber 6.

A feature of the construction indicated in FIG. I is that the pressure of the burnable gases which are produced acts on an annular piston 7 which floats on a liquid oxidizer supply 8 arranged between the chamber 9 and the combustion chamber 6. The oxidizer chamber is bound at its opposite end by a fixed or solid bottom 10 having nozzles or injectors 11 through which the oxidizer 8 is directed by the force of the gases as they are produced acting on the piston 7. The burnable gases which flow into the combustion chamber 6 and the injected oxidizer burn and produce thrust gases which are directed outwardly to the open end of the nozzle formation 12. By the arrangement of the oxidizer supply 8 behind the propellant charge in respect to the direction of flight of the missile 40, a particularly advantageous and simple construction of the drive system is obtained, especially with regard to the feed of the burnable gases which are produced and the feed of the oxidizer to the combustion chamber.

In the embodiment indicated in FIG. 2, there is provided a missile generally designated 44 which carries a plurality of ramjet engines 13, 13 which are, in the embodiment illustrated, arranged with their axes parallel about the central body portion 14. The propellant charge 45 includes a main propellant charge 1' and an auxiliary propellant charge 3' contained therewithin but separated therefrom by a burn-off insulation 2'. The propellant charge 46 is maintained in the rear end of the missile 44, and the gases which are produced from the propellant charge combination I and 3 are conveyed from the collecting zone 9', defined directly above the propellant charge 46, through the connecting lines 15, I5. Each connecting line I5 terminates in a nozzle I6 which is arranged to direct the gas axially along an elongated combustion chamber I7 of the associated ramjet engine 13. The gases are burned with compressed air which enters through air inlets or diffusers 18 arranged at the forward end of the combustion chamber 17 to draw air in through the chamber. The gases which are burned are then discharged through the thrust noz' zles 19.

In order to obtain as good a heat contact as possible between the auxiliary propellant charge 3 and the main propellant charge 1 and hence a good preparation of the burnable gases, it is advantageous to make the contact surfaces between these charges very large, that is, to form a high ratio between circumferential length and cross-sectional surface. As indicated in FIG. 3, for this purpose, the auxiliary propellant charge 3" may be profiled in a star-shaped configuration as a front burner and be enveloped by the main propulsion charge I both internally and externally. The burn-off insulation 2" between the two propellant charges I" and 3 serves to insure an exact front burn-off.

In FIG. 4, an alternate embodiment is shown wherein the auxiliary propulsion charge 3" and the main propulsion charge I"' are alternately arranged in spiral layers. FIG. 5 shows an arrangement in which the layers of the main charge 1"" and the auxiliary charge 3"" are arranged in concentric annular layers. And lastly, the arrangement of FIG. 6 shows the charges in the form of sectors which are alternately arranged proceeding radially. FIGS. 35 show front burner constructions, but the embodiment of FIG. 6 shows an internal burner arrangement and the area ratio between the main charge I""' and the auxiliary charge 3"" is in accordance with the heat requirement of the main propellant charge which is employed. A particularly suitable propulsion charge for the main charge is a solid propellant formed of a compound rich in hydrogen and carbon and which requires little heat for its transformation from the solid to the gaseous state.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What I claim is:

l. A method for producing burnable gases under pressure for thrust engines using a combination of two solid propellant charges, comprising arranging an auxiliary propellant charge of a high thermal efficiency directly adjacent a main propulsion charge of a low heat of fusion and evaporation, igniting and burning off (stoichiometrically) the auxiliary charge in a closed chamber and in a manner to cause the main charge to become simultaneously transformed into a different state by being fused, evaporated, and Sublimated without chemical change, and using the pressure of the gases generated by the burn-off of the auxiliary charge to conduct the gases formed by the combined charges to a combustion chamber for addition with an oxidizer for further combustion.

2. A method, according to claim 1, including conveying an oxidizer to the combustion chamber using the force of the gas pressure produced by the burning of the auxiliary charge.

3. A method, according to claim 1, wherein an oxidizer such as air is directed into the combustion chamber along with the gases of the combined charge.

4. A method for producing burnable gases under pressure for thrust engines using a combination of a solid main propellant charge having a low heat of fusion and of evaporation and a solid auxiliary propellant charge having a high thermal efficiency, comprisingarranging the auxiliary propellant charge adjacent to the main propellant charge in an enclosed space molecular structure free of chemical change, and collecting the gases generated by the bum-off of the auxiliary charge and employing the pressure of the collected gases for conveying them into. a combustion space. 

1. A method for producing burnable gases under pressure for thrust engines using a combination of two solid propellant charges, comprising arranging an auxiliary propellant charge of a high thermal efficiency directly adjacent a main propulsion charge of a low heat of fusion and evaporation, igniting and burning off (stoichiometrically) the auxiliary charge in a closed chamber and in a manner to cause the main charge to become simultaneously transformed into a different state by being fused, evaporated, and sublimated without chemical change, and using the pressure of the gases generated by the burn-off of the auxiliary charge to conduct the gases formed by the combined charges to a combustion chamber for addition with an oxidizer for further combustion.
 2. A method, according to claim 1, including conveying an oxidizer to the combustion chamber using the force of the gas pressure produced by the burning of the auxiliary charge.
 3. A method, according to claim 1, wherein an oxidizer such as air is directed into the combustion chamber along with the gases of the combined charge.
 4. A method for producing burnable gases under pressure for thrust engines using a combination of a solid main propellant charge having a low heat of fusion and of evaporation and a solid auxiliary propellant charge having a high thermal efficiency, comprising arranging the auxiliary propellant charge adjacent to the main propellant charge in an enclosed space and igniting and burning off the auxiliary charge in the enclosed space and transferring the heat generated thereby to the main charge for simultaneously completely transforming the solid main charge into the gaseous state and retaining its molecular structure free of chemical change, and collecting the gases generated by the burn-off of the auxiliary charge and employing the pressure of the collected gases for conveying them into a combustion space. 